package com.kuang.rw;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * @author luomingliang
 * @date 2021/5/17 20:30
 */
public class ReadWriteLockDemo {
    /**
     * 独占锁（写锁） 一次只能被一个线程战友
     * 共享锁（读锁） 多个线程可以同时占有
     * ReadWriteLock
     * 读-读 可以共存
     * 读-写 不能共存
     * 写-写 不能共存
     */
    public static void main(String[] args) {
//        MyCache myCache = new MyCache();
        MyCacheLock myCache = new MyCacheLock();
        //写入
        for (int i = 1; i <= 5; i++) {
            int temp = i;
            new Thread(()->{
                myCache.put(temp+"", temp+"");
            }, String.valueOf(i)).start();
        }
        //读取
        for (int i = 1; i <= 5; i++) {
            int temp = i;
            new Thread(()->{
                myCache.get(temp+"");
            }, String.valueOf(i)).start();
        }
    }
}

//加锁的
class MyCacheLock {

    private volatile Map<String, Object> map = new HashMap<>();
    //读写锁：更加细粒度的控制
    private ReadWriteLock lock = new ReentrantReadWriteLock();

    //存，写  写入的时候，只希望同时只有一个线程写
    public void put(String key, Object value) {
        lock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"写入："+key);
            map.put(key, value);
            System.out.println(Thread.currentThread().getName()+"写入OK");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.writeLock().unlock();
        }
    }

    //取，读  所有人都可以读
    public Object get(String key) {
        lock.readLock().lock();
        Object o = null;
        try {
            System.out.println(Thread.currentThread().getName()+"读取："+key);
            o = map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取OK");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.readLock().unlock();
        }
        return o;
    }
}

/**
 *  自定义缓存
 */
class MyCache {

    private volatile Map<String, Object> map = new HashMap<>();

    //存，写
    public void put(String key, Object value) {
        System.out.println(Thread.currentThread().getName()+"写入："+key);
        map.put(key, value);
        System.out.println(Thread.currentThread().getName()+"写入OK");
    }

    //取，读
    public Object get(String key) {
        System.out.println(Thread.currentThread().getName()+"读取："+key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName()+"读取OK");
        return o;
    }
}